1. Field of the Invention
The present invention relates generally to medical devices and methods. In one embodiment, the present invention relates to devices and methods for disrupting, collecting, and removing thrombus from blood vessels and other body lumens.
Thrombosis and atherosclerosis are common ailments which occur in humans and which result from the deposition of thrombus and clot on the walls of blood vessels. When hardened, such deposits are commonly referred to as plaque. Such deposits are most common in the peripheral blood vessels that feed the limbs of the human body and the coronary arteries which feed the heart. Stasis, incompetent valves, and trauma in the venous circulation cause thrombosis, particularly occurring as a deep vein thrombosis in the peripheral vasculature. When such deposits build-up in localized regions of the blood vessel, they can restrict blood flow and cause a serious health risk.
In addition to forming in the natural vasculature, thrombosis is a serious problem in xe2x80x9cartificialxe2x80x9d blood vessels, particularly in peripheral femoral-popliteal and coronary bypass grafts and dialysis access grafts and fistulas. The creation of such artificial blood vessels generally involves anastomotic attachment at at least one, and usually at at least two, locations in the vasculature. Such sites of an anastomotic attachment are particularly susceptible to thrombus formation due to narrowing caused by intimal hyperplasia, and thrombus formation at these sites is a frequent cause of failure of the implanted graft or fistula. The arteriovenous grafts and fistulas which are used for dialysis access are significantly compromised by thrombosis at the sites of anastomotic attachment and elsewhere. Thrombosis often occurs to such an extent that the graft needs to be replaced within a few years or, in the worst cases, a few months.
A variety of methods have been developed for treating thrombosis and atherosclerosis in the coronary and peripheral vasculature as well as in implanted grafts and fistulas. Such techniques include surgical procedures, such as coronary artery bypass grafting, and minimally invasive procedures, such as angioplasty, atherectomy, transmyocardial revasculaturization, and the like. In many of the surgical clinical approaches to removing unwanted material, the treatment site is accessed directly through a surgical incision. Of particular interest of the present invention, a variety of techniques generally described as xe2x80x9cthrombectomyxe2x80x9d have been developed. Thrombectomy generally refers to procedures for the removal of relatively soft thrombus and clot from the vasculature. Removal is usually achieved by mechanically disrupting the clot, optionally with the introduction of thrombolytic agents. The disrupted thrombus or clot is then withdrawn through a catheter, typically with a vacuum or mechanical transport device.
Thrombectomy generally differs from angioplasty and atherectomy in the type of occlusive material which is being treated and in the desire to avoid damage to the blood vessel wall. The material removed in most thrombectomy procedures is relatively soft, such as the clot formed in deep vein thrombosis, and is usually not hardened plaque of the type treated by angioplasty in the coronary vasculature. Moreover, it is usually an objective of thrombectomy procedures to have minimum or no deleterious interaction with the blood vessel wall. Ideally, the clot will be disrupted and pulled away from the blood vessel wall with no harmful effect on the wall itself.
While successful thrombectomy procedures have been achieved, most have required comprise between complete removal of the thrombosis and minimum injury to the blood vessel wall. While more aggressive thrombectomy procedures employing rotating blades can be very effective at thrombus removal, they can present a significant risk of injury to the blood vessel wall. Alternatively, those which rely primarily on vacuum extraction together with minimum disruption of the thrombus, often fail to achieve sufficient thrombus removal.
In work related to the present invention, an expansible macerator for safely breaking up or disrupting thrombus and other occlusive materials has been proposed. U.S. patent application Ser. No. 09/454,517 filed on Dec. 6, 1999 and entitled xe2x80x9cSystems and Methods for Clot Disruption and Retrieval,xe2x80x9d describes a catheter having an expansible positioning cage and a helical macerator positioned within the cage. The macerator can be separated from the surrounding cage so as to maintain separation between the macerator and a surrounding wall of the body lumen. This caged macerator represents a significant advancement in the art, as it allows disruption of soft clot while inhibiting trauma to blood vessels of varying diameters. However, as with all advances, still further improvements would be desirable. In particular, it may be beneficial to provide more aggressive and more rapid removal of clot material. It would also be helpful to allow the physician to selectively and controllably remove plaque or other more solid occlusive material during a thrombectomy, preferably using the thrombectomy catheter. It may also be beneficial to more uniformly urge the severed debris toward an aspiration port of the thrombectomy catheter.
In light of the above, it would be beneficial to provide improved devices, systems, methods, methods for manufacture, and kits for removing thrombus material from the vasculature and other body lumens. It would be particularly desirable to provide improved techniques for advancing a guidewire or guide catheter, positioning a treatment catheter across the blocking occlusion, isolating the treatment site, and further treating the occlusion while minimizing or eliminating any distal emboli. An improved procedure would also benefit from having a device that can rapidly aspirate the occlusive material from the body lumen. Optionally, these improved devices and methods might be used to treat a total occlusion as the treatment device is being advanced through the occlusion, facilitating placement of a wire across the occlusion so that further treatment can be easily commenced. Device and methods which allow creation of a channel through a total occlusion for placement of a guidewire would also be advantageous, as would improved debulking of stenotic tissues.
Some or all of these objectives may be met by the device and methods of the present invention.
2. Description of the Background Art
As mentioned above, systems and methods for clot disruption and removal related to the present invention are described in U.S. patent application Ser. No. 09/454,517. A related mechanical pump for removal of fragmented matter and methods was described in U.S. patent application Ser. No. 09/590915, filed on Jun. 9, 2000. A further related method and system for reinfusing filtered body aspirates is described in U.S. Provisional Patent No. 60/174,108, filed on Dec. 31, 1999.
A cutting stent with a flexible tissue extractor is described in U.S. Pat. No. 6,036,708. A compressible/expandable atherectomy cutter is described in U.S. Pat. No. 5,224,945. Unitary removal of plaque is described in U.S. Pat. No. 5,665,098. A method for performing a partial atherectomy is described in U.S. Pat. No. 5,282,484, while an atherectomy device having a helical blade and a blade guide is described in U.S. Pat. No. 5,569,277. A catheter arthrotome is described in U.S. Pat. No. 5,178,625. A surgical apparatus for transurethral resection is described in U.S. Pat. No. 3,320,957. A vessel deposit sharing apparatus is described in U.S. Pat. No. 5,527,326.
A coiled stent with locking ends is described in U.S. Pat. No. 5,725,549. A medical instrument with a slotted memory metal tube is described in U.S. Pat. No. 5,885,258. A method for manufacturing a tubular medical device is described in U.S. Pat. No. 6,027,863. The following U.S. Patent Nos. may also be relevant: U.S. Pat. Nos. 6,010,449; 5,968,064; 5,741,270; 5,766,191; 5,569,275; 5,501,694; 5,795,322; 5,904,968; 5,224,945; 5,312,425; 5,330,484; and 6,022,336.
All of the above references, and any and all other references cited in this application, are incorporated herein by reference in their entirety for all purposes.
The present invention provides improved devices, methods, kits, methods for fabrication, and the like, for removing thrombus from the vasculature. The invention generally makes use of cooperating radially expansible shearing members, each shearing members often being in the form of an expansible basket. The exemplary baskets comprise helically oriented struts, with the struts of each shearing member extending with a uniform circumferential direction. The struts will often be independently flexible between proximal and distal portions of the shearing members, which can allow the shearing the members to flex axially to follow axially curving body lumens. The inner basket may be rotatably driven within the outer basket, and may optionally be coupled to an axial pump extending proximally from the shearing members. The outer basket may be coupled to a catheter body to avoid excessive tissue trauma to the body lumen, and the helical struts of the shearing members can by helically counterwound, so that the inner struts may slide substantially continuously across the outer struts. The inner and outer baskets may both radially expand selectively, independently and/or with a single actuator. The resulting shearing action is sufficiently aggressive for highly effective thrombectomy, while use of a rotationally static and axially flexible outer basket may provide a safe, limited, and controllable treatment.
In a first aspect, the invention provides a thrombectomy catheter comprising a flexible tubular body having a proximal end and a distal end. An outer shearing member is attached near the distal end, the outer member having a perforate inner surface. An inner shearing member is rotatably disposed within the outer member, the inner member having a proximal portion, a distal portion, and a circumferential series of struts extending therebetween. The struts can flex to slide across the inner surface of the outer shearing member when the inner shearing member rotates.
Optionally, the inner member may rotate about an axis, and the inner and outer shearing bodies may be sufficiently flexible to deflect the axis laterally when the outer shearing member is expanded to engage a surrounding vessel and the inner member rotates therein. The struts may uniformly coil helically in a first circumferential orientation so that rotation of the inner shearing member toward the first circumferential orientation consistently urges sheared occlusive material proximally. The inner shearing member may comprise tube material, the struts being separated by cut surfaces between adjacent tube material portions. The outer shearing member may comprise outer tube material having a proximal outer portion, a distal outer portion and a circumferential series of outer struts extending helically therebetween, with the struts being separated by cut outer surfaces between outer adjacent tube material portions. The struts may be affixed together at the proximal portion and at the distal portion, and may flex independently therebetween.
The struts may be helically oriented with a local pitch of the struts varying axially along the struts. The local pitch can increase toward the proximal and distal portions sufficiently to inhibit excessive separation between adjacent struts when the outer shearing member flexes axially. The struts may have protrusions which inhibit sliding of thrombus axially between cooperating edges of the inner and outer shearing bodies. At least one expansion actuator may extend proximally from the shearing members so that the inner and outer shearing members can be radially expanded in situ. Axial translation of an expansion actuator may selectively radially expand the inner and outer shearing members concurrently.
A distally oriented occlusion penetrator may be disposed adjacent the distal end of the shearing members. The occlusion penetrator may comprise one or more end cutters that rotate with the inner shearing member and are exposed distally of the outer shearing member to help advance the shearing members distally through occlusive material and within a body lumen. Alternative occlusion penetrators include a shaft extendable distally of the shearing members, the shaft axially oscillating through occlusive material without penetrating through a vessel wall. An intravascular ultrasound sensor can be used to measure thrombus, monitor thrombus removal, and/or verify the treatment.
It may also be desirable to attach a porous or non-porous coverings or coatings to at least one shearing member, particularly to the outer shearing member. Such a covering or coating may extend between the struts of a shearing member or positioning cage when the shearing member or positioning cage expands, and can be made from PTFE woven material, filter material (metallic or polymeric), braid material (metallic or polymeric), mesh, polymeric coatings, and the like. The coatings can be applied to the outer basket through a dipping process. Alternatively, the coverings may be applied to the outer basket using cyanoacrylate or other adhesives, thread or suturing, welding or bonding, or the like. Such coatings may be disposed along a distal and/or proximal region of the expandable perforate shearing member, and may inhibit embolization of fragmented thrombus, constrain a treatment fluid or fluid stream, and the like.
In another aspect, the invention provides a thrombectomy catheter comprising a flexible tubular body having a proximal end and a distal end. A flexible drive shaft is rotatably disposed within the tubular body. An outer shearing member attached near the distal end of the tubular body has a circumferential series of independently flexible outer struts with inner surfaces. An inner shearing member is rotationally driven by the drive shaft within the outer member, the inner member having a circumferential series of independently flexible inner struts, the inner struts having outer surfaces which slide across the inner surfaces of the outer struts when the inner shearing member rotates, at least one member of the group comprising the inner struts and the outer struts being helically oriented.
Optionally, the inner and outer shearing members can each have proximal portions and distal portions, the struts of each shearing member affixed together at the proximal and distal portions and extending independently therebetween so that the shearing members flex axially primarily along the struts. A proximal housing may be coupled to the tubular body, the housing having a motor drivingly engaging the drive shaft. The drive shaft may engage the distal portion of the inner shearing member and be axially translatable relative to the outer tubular member from adjacent the proximal housing. An axial bearing surfaces of the outer and inner shearing members can cooperate to effect concurrent radial expansion of the inner and outer shearing members when the drive shave translates axially.
In another aspect, the invention also provides a method for forming a thrombectomy catheter. The method comprises providing a first tube having a proximal end and a distal end with a central region therebetween, the tube comprising a tube material. The central region of the first tube is cut axially so as to define a circumferential series of independent deformable struts, the struts comprising the tube material. The first cage can be positioned coaxially with a second resiliently deformable cage, and a drive can be attached for rotating at least one of the cages within a blood vessel for shearing of thrombus between the cages.
In another aspect, the invention comprises a method for removing thrombus from a blood vessel of a patient. The method comprises introducing a distal portion of a catheter into the blood vessel. The distal portion of the catheter is positioned adjacent the thrombus from outside the patient by manipulating a flexible body of the catheter. Inner and outer shearing members of the catheter are radially expanded within the blood vessel, the inner shearing member is rotated within the outer shearing member to shear the occlusive material therebetween.